I am so new to all the technical aspects of photography. I have been using my Panasonic Z18 just ia. I am trying to learn manual and playing with aspect ratio and shutter speed(etc). Please tell me what is the best iso to use generally. My book does not tell me when to use what with his. At the risk of sounding like a complete amateur (o.k. so I am)

ISO means the film speed. The higher the ISO, the faster the film speed. Meaning the shorter the exposure time you can use to get the same image. That is as far as the theory goes. Here, highest ISO means fastest shutter and looks very good, but in practice it is not so simple. In digital cameras, higher ISO means more noise. Thus, yous pictures can either lack fine details due to noise suppression or look all grainy. Thus, as far as digital photography goes, I prefer to keep my ISO to the minimum, unless a fast shutter speed is really needed. Most recent cameras in non-DSLR range give clean results up to ISO200. Noise starts becoming prominent at ISO400 and above. However, this also depends on every situation, particularly in terms of lighting conditions. Also, from what I know, the tonal/dynamic range is also somewhat dependent on ISO, and most cameras perform best around ISO200. Again, this varies from camera to camera.

My dad has the FZ18, and it's noisier than my FZ28....
So, I dont know, but if you zoom in alot at the PC, youll stick at 100ISO, if you're not zooming in, or making big prints (40x30cm) you can use 200ISO. with 400ISO I got pretty bad results at 40X30 CM without NR..

Hi Nancy, as the others have said, the ISO number refers to the sensitivity of the sensor. The bigger the number, the more sensitive it becomes, which is useful if you need a veryt fast shutter speed to freeze action, or more likely, are shooting in low light and want to avoid blur.

BUT as the others have said, the more you increase the ISO, the worse the quality becomes. Please visit the High ISO Noise results page of any of my Panasonic reviews and you'll see exactly what happens at high ISOs. It ain't pretty!

So the rule for the best quality is to use the lowest ISO possible, such as 80 or 100, and only increase it when you need a faster shutter to freeze action or avoid blur.